1. Field of the Invention
The invention relates to the art of rendering images. The invention finds particular application where the colorimetry of an image is unknown.
2. Description of Related Art
Modern electronic image files contain identifying information. The identifying information is usually stored in what is called a header section of the image files. The header can identify a means with which the image was created. For example, the header can list an authoring device by manufacturer and model number as well as describe configuration settings that were used during authoring. Additionally, the header can describe a color space the authoring device operates in. The header information can be used by image processing equipment to properly interpret image data within the file and automatically ensure proper rendering. The header information is most important when an image created on a first image processing system is rendered on a second image processing system. The header information is especially important when the second image rendering system is totally unaware of, and disconnected from, the first image processing system or authoring device. For example, when an image is anonymously posted and retrieved from a computer network or bulletin board, such as, for example, the INTERNET, header information is especially important. Modern image processing equipment depends on the header information in order to accurately and automatically render an image created with a first device in the first color space with a second device in a second color space.
Unfortunately, not all image files contain an identifying header section. These older image files, or image files created on authoring devices that do not provide complete identifying information are referred to in this document as legacy images. When these legacy files are being processed, the image processing equipment must request operator intervention in order to properly identify and render the image. Often, the operator is presented with a list of possible sources for the data. For example, while processing a CMYK (cyan, magenta, yellow, key (black)) image of unknown origin, the user may be asked to pick the device the image could have been created with, from a list including Specification Web Offset Printing (SWOP) devices, JapanColor devices, Euroscale devices, and/or other devices. As another example, while processing scanned RGB files, choices may include the scanner, scanned medium (e.g photographic, lithographic), and tone scale (gamma) correction.
There are problems with this image source identification technique. One problem is that often the operator does not know where the file came from. In these cases the operator is forced to guess which of the listed devices was used to create the image. Currently, after guessing at image authorship, the user must make a test print in order to verify his guess. If after examining the test print, the user determines that his guess was incorrect, another guess is made and another test print is created. Color printing can be a relatively slow process. For example, color printing is slower than black and white laser printing. Additionally, in at least some cases, the list of possible image authoring devices is quite long. Therefore, the process of guessing at authorship and generating test prints can be an expensive, time-consuming, aggravating, iterative process.
Recently, automated methods have been proposed to analyze legacy images and automatically surmise the images authorship and colorimetry. However, these automated methods have not as yet been perfected. For, example, in some instances these automated methods are able to reduce the length of the list of possible authoring devices, but are unable to make a final selection. Furthermore, these automated methods are not always available.
Therefore, additional legacy image authorship device identification methods are needed. In the best of situations, additional methods are needed to allow a user or operator to approve the authorship selection arrived at by the automated methods. In less sophisticated systems additional methods are needed to allow a user to quickly sort through a shortened list of choices arrived at by the automated methods. In the least sophisticated systems additional methods are needed to allow a user to quickly sort through the entire list of possible authoring devices.
Therefore, a method of softproofing, or previewing an image on a display device, for the purpose of evaluating the image and determining the colorimetry of the image, has been developed. The method can be performed using a color image processor and an associated display device. The method comprises the steps of opening an electronic image file containing an image, indicating a possible source for the image file, setting a currently indicated source parameter to reflect the indicated source, transforming the image by combining the image with a source profile for the currently indicated source and a display device profile for the associated display device and displaying the transformed image. The transformations or combinations serve to allow the image to be displayed, as it would appear if the currently indicated source were an actual source of the image.
The displayed image is then evaluated to determine if the currently indicated source should be assigned to the image.
Additionally the invention includes a color image processor system comprising a display device and a color image processor for performing the method. The system comprises a source device emulator for accepting an image file and transforming an image from the image file by combining the image with colorimetry information from an indicated source device profile. The color image processor also includes a display device interface for further transforming a version of the image by combining the version of the image with colorimetry information from a display device profile associated with the display device so that the image can be properly displayed on the display device.
One advantage of the present invention is that it allows a display device such as, for example a computer CRT to be used to test the accuracy of guesses about the authorship and colorimetry of a legacy image file.
Another advantage of the present invention is that it eliminates the need to use relatively slow rendering devices, such as, for example, color printers, to test the accuracy of guesses about the authorship and colorimetry of a legacy image file.
Another advantage of the present invention is that it allows a plurality of guesses about the authorship and colorimetry of a legacy image to be quickly evaluated in a side-by-side comparison.
Another advantage of the present invention is that it allows a user to determine the correct or appropriate colorimetry of a legacy file in less time than other methods and systems do.
Another advantage of the present invention is that it allows a user to determine the correct or appropriate colorimetry of a legacy file without consuming print media, such as paper.
Another advantage of the present invention is that it allows a user to determine the correct or appropriate colorimetry of a legacy file without wasting printing materials such as, for example, toners or colorants.
Yet another advantage of the present invention is that it allows a user to determine the correct or appropriate colorimetry of a legacy file at a reduced cost of time and materials.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.